Innate lymphoid cells in allergy

Published on February 29, 2024   41 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

Other Talks in the Series: Allergy - From Basics to Clinic

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Hello, my name is Shigeo Koyasu from Keio University. I'll talk about the innate lymphoid cells in allergic diseases.
So, the contents are in five rows. I'll start with what innate lymphoid cells (ILCs) are and then an overview about the allergic diseases and ILCs. Then, I'll talk about the role of ILC2 in allergic diseases with our own data. I'll briefly mention about the role of other ILCs in allergic diseases and then, I'll conclude my talk.
So, what are ILCs? ILCs are lymphocytes without Rag-dependent rearranged antigen receptors. So, they don't have any antigen receptors. The first innate lymphoid cells discovered was natural killer (NK) cells that were found in 1975, and the next one was lymphoid tissue inducer (LTi) cells found in 1997, which plays a role during the fetal stages to induce lymph nodes and Peyer's patches, and so on. Those are the so-called first-generation innate lymphoid cells,
but in 21st century, we found three new types of innate lymphoid cells. We know that there are three types of helper T-cells, Th1, Th17, and Th2 with T-cell receptors. Th1 cells produce interferon-gamma (IFNγ), which act on macrophages (Mϕ) and then act on fighting against the intracellular microbes and viruses. Th17 cells produce IL-17 and IL-22 which mostly act on epithelial cells, which plays an important role for immunity against fungi and Escherichia bacteria, such as EHEC and ETEC. Th2 cells producing IL-5 and IL-13 induce eosinophilia and goblet cell hyperplasia, which play an important role in immunity against helminth. Those are in adaptive immunity, but during the innate immune phase, as I said, NK cells was found in 1975, which are able to produce IFNγ as Th1 cells. Around 2008-2009, people found LTi-like cells in adult intestine which do not have T-cell receptors, but are able to produce IL-17 and IL-22 as Th-17 cells. Next, innate lymphocytes they found was the T-bet^+ EOMES^- innate lymphocytes, which are able to produce IFNγ, but possess very low level of cytotoxicity. So, therefore, we now know that NK cells correspond to CTL (cytotoxic lymphocytes) and T-bet^+ EOMES^- cells correspond to Th1 cells. Lastly, natural helper cells, which we named, expressing GATA3 was discovered, which again lack T-cell receptors, but are able to produce IL-5 and IL-13 as Th2 cells. So, pros for those cells are they actually play an important role for immunity against various invading microbes, fungi, and helminths, but cons are they induce various types of acute and chronic inflammation. In 2013, people working in this field decided to call γ producers as Group 1 ILC or ILC1, type 2 cytokine producing cells Group 2 ILCs or ILC2, and IL-17, IL-22 producing cells as Group 3 ILCs or ILC3.